1. Field of the Invention
The present invention relates to a bus bar having a geometry designed for filtering desired signal frequencies.
2. Brief Description of the Prior Art
The prior art has already proposed bus bars configured to create a high capacitive region of low impedance for filtering high frequency noise and attenuate voltage transients. For that purpose, a region of high static capacitance is formed by inserting a high dielectric material in the form of wafers, chips or disks between two electrically conducting plates. For example:
U.S. Pat. No. 4,436,953 granted to Gottlieb on Mar. 13, 1984 describes miniature bus bar assemblies which incorporate discrete capacitive elements having a high dielectric constant. These capacitive elements are preferably metallized ceramic wafers bonded between a pair of bus bar conductors.
U.S. Pat. No. 4,440,972 (Taylor) issued on Apr. 3, 1984 proposes miniature bus bars in which capacitor ribbons with discrete capacitive elements are retained within the insulating layer. These capacitor ribbons are mounted between a pair of bus bar conductor plates with the capacitive elements placed in electrical contact with the plates.
U.S. Pat. No. 4,584,768 granted to Tosti on Apr. 29, 1986 relates to a method for manufacturing a highly capacitive multilayer conductive bar. Again, ceramic chips are used to improve the capacitance. These chips are placed within the layers of the conductive bar.
U.S. Pat. No. 5,185,690 (Hernandez) issued on Sep. 24, 1991 discloses a bus bar including conductive layers and a high capacitance flexible dielectric sheet material between these conductive layers. The high capacitance dielectric sheet comprises high dielectric chips or pellets of relatively small area and thickness arranged in a planar array. These high dielectric constant chips are spaced apart by a small distance.
U.S. Pat. No. 5,365,424 granted to Deam et al., on Nov. 15, 1994 suggests the use of a low impedance (high capacitance) bus structure involving a laminated plate assembly. This patent mentions that the inductive impedance substantially attenuates the high frequency response of a bus.
The above prior art references present no high frequency model for any structure, and the performance of these structures is likely to be very irregular from the frequency response and filtering points of view. Also, these structures will not enable the construction of a bus bar capable of producing desired frequency attenuation for high frequency signals while conducting DC signal without attenuation.
Also, low pass filters are currently used in electrical circuits to suppress noise. In high impedance and high frequency circuits, pi-network filters are widely used. A pi-network includes two shunt capacitors and an inductor connected in series between the two capacitors. U.S. Pat. No. 4,853,659 granted to Kling on Aug. 1, 1989 describes a planar pi-network filter assembly. This filter assembly comprises capacitive structures formed on opposing surfaces of a planar inductive member. Each capacitive structure comprises a ground electrode section, a dielectric layer and a signal electrode. Preferably, the inductive member is made of ferrite material. The combination forms a capacitor-inductor-capacitor pi-network.
An object of the present invention is to provide a laminated conductor assembly presenting a desired frequency-filtering feature obtained by manipulating the geometry of the conductor(s).
More specifically, in accordance with the present invention, there is provided a laminated conductor assembly comprising an input section, an output section, and a superposition of alternate electrically conducting and electrically insulating layers. The electrically conducting layers present a geometry which defines both capacitive and inductive structures, and these capacitive and inductive structures form, between the input and output sections, a capacitive and inductive frequency-filtering circuit.
In accordance with a preferred embodiment of the laminated conductor assembly, the electrically conducting layers comprise respective, superposed first end portions for defining first capacitive structures, respective, superposed second end portions opposite to the first end portions for defining second capacitive structures, and respective narrower bridge portions for interconnecting the first and second end portions of the corresponding electrically conducting layers and for defining respective inductive structures. Advantageously, at least a part of the narrower bridge portions are laterally offset with respect to each other.
The present invention further relates to a laminated direct current bus bar, comprising an input section, an output section, and a superposition of alternate electrically conducting plates and electrically insulating films. This superposition comprises a first electrically conducting ground plate, an electrically conducting positive plate, an electrically conducting negative plate, a second electrically conducting ground plate, a first electrically insulating film interposed between the first ground plate and the positive plate, a second electrically insulating film interposed between the positive plate and the negative plate, and a third electrically insulating film interposed between the negative plate and the second ground plate. The first ground plate, the positive plate, the negative plate and the second ground plate have a geometry which defines both capacitive and inductive structures, and these capacitive and inductive structures form, between the input and output sections, a capacitive and inductive frequency-filtering circuit.
According to a preferred embodiment of the laminated bus bar, the first ground plate, the positive plate, the negative plate and the second ground plate comprise respective, superposed first end portions for defining first capacitive structures, respective, superposed second end portions opposite to the first end portions for defining second capacitive structures, and respective narrower bridge portions for interconnecting the first and second end portions of the corresponding plates, these narrower bridge portions defining respective inductive structures.
Preferably, the narrower bridge portions of the positive and negative plates are laterally offset with respect to each other and with respect to the narrower bridge portions of the first and second ground plates.
According to another preferred embodiment:
the input section comprises a tab of the first end portion of the positive plate and a tab of the first end portion of the negative plate;
the output section comprises a tab of the second end portion of the positive plate and a tab of the second end portion of the negative plate;
the first ground plate, the positive plate, the negative plate and the second ground plate have respective first and second ends;
the tab of the first end portion of the positive plate is a laterally extending tab situated at the first end of the positive plate;
the tab of the first end portion of the negative plate is a laterally extending tab situated at the first end of the negative plate;
the tab of the second end portion of the positive plate is a laterally extending tab situated at the second end of the positive plate; and
the tab of the second end portion of the negative plate is a laterally extending tab situated at the second end of the negative plate.
In accordance with a further preferred embodiment of the laminated bus bar, the first and second ground plates are electrically interconnected, the first end portion of the positive plate and the first end portion of the first ground plate define with the first film a first shunt capacitor structure, the first end portion of the positive plate and the first end portion of the negative plate define with the second film a second shunt capacitor structure, the first end portion of the negative plate and the first end portion of the second ground plate define with the third film a third shunt capacitor structure, the narrower bridge portion of the positive plate forms a first inductor structure, the narrower bridge portion of the negative plate forms a second inductor structure, the narrower bridge portions of the first and second ground plates form a third inductor structure, the second end portion of the positive plate and the second end portion of the first ground plate define with the first film a fourth shunt capacitor structure, the second end portion of the positive plate and the second end portion of the negative plate define with the second film a fifth shunt capacitor structure, and the second end portion of the negative plate and the second end portion of the second ground plate define with the third film a sixth shunt capacitor structure.
In accordance with a further preferred embodiment of the laminated bus bar, the first and second ground plates both have first and second ends and are longer than the positive and negative plates and the first, second and third films, the first ends of the first and second ground plates are interconnected and the second ends of the first and second ground plates are interconnected.